THE INTERPLAY OF ELECTRONIC AND NUCLEAR MAGNETISM IN PTFEX AT MILLIKELVIN, MICROKELVIN, AND NANOKELVIN TEMPERATURES

We have measured ac susceptibility, nuclear magnetic resonance, and nu clear heat capacity of two PtFex samples with concentrations of magnet ic impurities x = 11 ppm and 41 ppm at magnetic fields (0 +/- 0.05) mT less than or equal to B less than or equal to 248 mT. The susceptibil ity data have been measured at temperatures of 0.3 mu K less than or e qual to T less than or equal to 100 mK, no hint for nuclear magnetic o rdering could be detected to a temperature of 0.3 mu K. The nuclear he at capacity data taken at 1.4 mu K less than or equal to T less than o r equal to 10 mK show enhanced values which scale with x at low polari zation. This effect is described by a model assuming an internal magne tic field caused by the impurities. No indication for nuclear magnetic ordering could be detected to 1.4 mu K. The nuclear magnetic resonanc e experiments have been performed on these samples at 0.8 mu K less th an or equal to T less than or equal to 0.5 mK and 2.5 mT less than or equal to B less than or equal to 22.8 mT as well as on three other sam ples with x = 5, 10, 31 ppm in a different setup at 40 mu K less than or equal to T less than or equal to 0.5 mK and at 5.4 mT less than or equal to B less than or equal to 200 mT. Spin-lattice and effective sp in-spin relaxation times tau(1) and tau(2) of Pt-195 strongly depend on x and on the external magnetic field. No temperature dependence of tau(1) and tau(2) could be detected and the NMR data, too, give no hi nt for nuclear magnetic ordering to 0.8 mu K.